GB2451719A

GB2451719A - Formaldehyde-free binder

Info

Publication number: GB2451719A
Application number: GB0807777A
Authority: GB
Inventors: Carl Hampson
Original assignee: Knauf Insulation Ltd
Current assignee: Knauf Insulation Ltd
Priority date: 2007-08-03
Filing date: 2008-04-29
Publication date: 2009-02-11
Anticipated expiration: 2028-04-29
Also published as: CA3063260A1; EP2176183B1; CL2008002297A1; US20160002441A1; HRP20200574T1; AU2008285696A1; US20140008563A1; EA201000279A1; EA201490282A1; EA035179B1; JP2019183172A; US9039827B2; HUE049984T2; DK2176183T3; LT2176183T; CN101821212A; US8940089B2; US20140312260A2; PT2176184T; US8979994B2

Abstract

A substantially formaldehyde-free binder solutions having a pH greater than 6, comprising a carbohydrate, an acid precursor derivable from an inorganic salt and a nitrogen source. Typically, the carbohydrate is a reducing sugar, especially dextrose. The acid precursor may comprise a species selected from sulphates, phosphates and nitrates and may comprise an ammonium salt. A material comprising a collection of loose material and the substantially formaldehyde-free binder is also disclosed. The loose material may comprise mineral fibres, such as those used for thermal insulation, or may be wood board. A further material comprising loose matter and a substantially formaldehyde-free binder is also described wherein the material comprises more than 500 mg/kg of species selected from sulphates, phosphates and nitrates. The binder may comprise melanoidins. Methods of manufacturing a binder solution and a product containing loose matter are also disclosed.

Description

1 2451719

BINDERS

This invention relates to binders, particularly for the manufacture of mineral wool insulation (for example glass wool or stone wool insulation).

WO 2007/014236 (incorporated herein by reference) relates to binders, including binders comprising Maillard reactants. One particular binder disclosed is based on a triammonium citrate -dextrose system derived from mixing dextrose monohydrate, anhydrous citric acid, water and aqueous ammonia.

One of the many advantages of this binder system is that it is formaldehyde free.

One aspect of the present invention provides a binder in accordance with claim 1; further aspects of the inventions are defined in other independent claims.

The dependent claims define alternative and/or preferred embodiments.

Binder solution in accordance with the present invention may be "substantially formaldehyde free", that is to say that they liberates less than 5 ppm formaldehyde as a result of drying and/or curing (or appropriate tests simulating drying and/or curing). Such binder solutions are preferably "formaldehyde free", that is the say they liberate less than 1 ppm formaldehyde in such conditions.

Products in accordance with the invention which incorporate binders (for example insulation materials) may be "substantially formaldehyde free", that is to say that they comprise less than 5 ppm or less than detectable limits of free formaldehyde and/or consist of materials which together comprise less than these amounts of free formaldehyde and/or release levels of formaldehyde in standardised tests adapted to simulate their ordinary use which allows them to be classified as having no or undetectable levels of formaldehyde release.

It has been found that binders according to the present invention may have at least equivalent and indeed improved properties compared to, for example, the

I

triammonium citrate -dextrose system of WO 2007/0 14236. WO 2007/014236 teaches binder systems based, inter alia, on a combination of a carbohydrate (for example a reducing sugar), ammonia and a carboxylic acid and suggests that a Maillard type reaction may form the basis of the curing chemistry. It would have been thought that the nature of the acid used would have a significant effect upon the properties of the cured binder, particularly if the acid precursor and/or a derivative therefrom is incorporated into the structure of the cured binder. It is thus surprising that an acid precursor derivable from an inorganic salt should provide a suitable acid precursor in an otherwise apparently similar binder system.

An acid precursor derivable from an inorganic salt may have significant advantages in terms of cost, availability and ease of handling. A particular advantage can be achieved by use of one or more inorganic ammonium salts, for example, an ammonium sulphate or an ammonium phosphate. An ammonium salt may provide the or part of the acid precursor and/or the or part of the source of nitrogen and/or the or part of a pH control system. An ammonium nitrate may also work; however, ammonium nitrate may oxidise aldehyde groups of the carbohydrate (for example in the case of dextrose) and/or require precautions to avoid explosions.

An ammonium sulphate is particularly advantageous but ammonium phosphate may be used in addition to or instead of this. Ammonium phosphate may be mono ammonium phosphate, di ammonium phosphate or tn ammonium phosphate; it may be an ammonium hydrogen phosphate.

The acid precursor, particularly when this consists essentially of inorganic ammonium salt(s), may make up * at least 5%, preferably at least 7%, more preferably at least 9% by dry weight of the uncured binder solution; and/or * less than 2O%, preferably less than 18%, more preferably less than 16% by dry weight of the uncured binder solution.

The binder may comprise between 5%-25%, preferably 10% to 20 %, more preferably 15% to 20% by dry weight of acid precursor (particularly where this is an inorganic ammonium salt) to carbohydrate (particularly when this is a sugar).

Prior art phenol formaldehyde binder systems for mineral wool insulation have been used with the addition of about 2% by weight ammonium sulphate as a curing agent. However, the chemistry of such phenol formaldehyde binder systems is not comparable to the binder systems of the present invention.

Preferences for the pH of the binder are: Preferred More preferred Most preferred pHof binder at least in the state in which the binder is applied to a material to be bound and/or recovered in a waste water recuperation system. Such a neutral or alkaline pH of the binder may alleviate problems of corrosion of manufacturing equipment which has been encountered with some essentially acidic prior art binder systems. When cured, the binder may become acidic during the curing process. However, equipment corrosion considerations are less significant in this case due to the minimal contact between the manufacturing equipment and the binder when in this state. The pH of the binder may be less than or equal to 13, preferably less than or equal to 12.

The carbohydrate may comprise a monosaccharide, for example in its aldose or ketose form. Preferably, the carbohydrate comprises a sugar, more preferably a reducing sugar or a reactant that yields a reducing sugar in situ under thermal curing condition; it may comprise glucose (ie dextrose). The carbohydrate may comprise a carbohydrate having a reducing aldehyde.

The binder composition may be provided in the form of an aqueous solution; it may contain free ammonia or excess ammonia in solution. A neutral or alkaline pH of the binder may be generated by an excess of alkaline groups compared with acid groups present in the binder solution, for example, due partially or substantially to the presence of ammonia in the solution.

The acid may comprise: a sulphuric acid, a phosphoric acid, a nitric acid or a weak acid.

Precursors for and/or reactants which give the materials referred to may be used.

Preferably, the binder is derived essentially from a carbohydrate and an inorganic ammonium salt in aqueous solution.

The source of nitrogen may be an amine reactant; it may be derivable from the same source as the in acid precursor, for example, from an inorganic ammonium salt.

Binders which comprise or consist essentially of the components described herein may include additives, for example, additives selected from: silanes, mineral oils, coupling agents, silicones, surfactants, hydrophilic additives, hydrophobic additives, waxes and substances useful for controlling the pH (e.g. ammonium hydroxide). Ammonium hydroxide when used, and indeed other additives, may provide the and/or an additional source of nitrogen.

Preferably, the total quantity of additives (excluding ammonia) is less than 5 % by weight (excluding the weight of water present), more preferably less than 3% or less than 2% by weight.

The binder may be curable; it may be cured, for example in a curing oven; it may form a thermoset binder. In its cured form, the binder may: comprise melanoidins; be thermoset; be water insoluble or substantially water insoluble.

The binder solution may be substantially colourless; upon curing, the binder may take on a dark colour, particularly a dark brown colour. The cured product may be dark in colour, particularly dark brown in colour. The binder may be free of proteins; it may be free of cellulosic feedstock.

The reaction of the binder upon curing may be essentially a Maillard type reaction as described for example in US Patent Application 20070027283 or The binder may be formulated by combining: * A carbohydrate; * An acid precursor derivable from an inorganic salt; * A source of nitrogen; and * water.

The formulation may comprise optional or additional ammonia provided in the form of an aqueous ammonia solution.

Forming the binder solution from a carbohydrate and an acid precursor comprising an inorganic ammonium salt provides one particular advantageous preparation method. This may be achieved in a simple mixing chamber which may be open and/or at atmospheric pressure. The carbohydrate and/or the acid precursor may be added in powder or liquid form. The preparation is preferably carried out at room temperature. Preferably it is not necessary to supply heat to prepare the binder solution; nevertheless, the binder solution may be heated during its preparation, for example to a temperature with the range 20°C to 80°C, particularly where this facilitates dissolving and/or mixing of its ingredients.

The binder solution may comprise: * at least lO%, 15% or 18% solids and/or * less than 70% or 60% (particularly in the case of wood board applications) or less than 50%, 40% or 20% solids (particularly in the case of mineral fibre insulation applications) determined as bake out solids by weight after drying at 140 °C for 2 hours.

The collection of loose matter bound together by means of the binder solution may comprise materials selected from: fibres, fibrous materials, mineral fibres, glass fibres, stone wool fibres, cellulosic fibres (including wood fibres, wood shavings, wood particles and sawdust), particles, woven or non-woven materials, loosely assembled materials.

The loose matter may be shaped and/or dimensioned and/or moulded with the aid of the binder. The material produced may be selected from: a thermal insulation material, a mineral fibre product, a wood board product (including chip board, orientated strand board, particle board, medium density fibre board, wood facing products), foundry sands.

Particularly in the case of mineral fibre materials, the binder solution may be sprayed on to the fibres, for example between formation of the fibres and collection of the fibres to form a batt. The fibres may be at a temperature in the range 20 °C to 100 °C when the binder is applied. Particularly in the case of wood boards products, the binder and the loose matter may be mechanically mixed, for example by tumbling.

The binder solution may have a viscosity appropriate for application by spraying or pouring. Its viscosity at 20°C may be: * Less than about 1.5 Pa.s, preferably less than about 1 x 10-2 Pa.s; and/or * Greater that about 2 x i0 Pa.s, preferably greater than about 5 x i0 Pa.s Curing of the binder may occur in a curing oven, for example using forced hot air circulation; it may occur in a press. Curing may comprise a dehydration of the binder; it may comprise a polymerisation. Curing may comprise a bulk polymerisation reaction. Curing may carried out for duration of 20 minutes or less, preferably 10 minutes or less.

Particularly in the case of mineral fibre insulation products, the curing temperature and time may be selected as a function of the product density and/or thickness. The curing oven in such cases may have a plurality of heating zones having temperatures within the range 200 °C to 350 °C (typically 230°C to 300 °C). A thin, low density product (12 kg/rn3 or less) may be cured by passing through the curing oven in as little as 20 seconds; a thick, high density product (80 kg/rn3 or more) may require a passage of 15 minutes or more in the curing oven. The product may reach a temperature in the range °C -220 °C during the curing process.

The binder in its uncured state may comprise the following levels of sulphates, phosphates and/or nitrates by dry weight: * Greater than 2.5%, 3% or S%; and/or * Less than 25%, 22%, or 20% Finished materials manufactured using binder systems according to the present invention may have residual levels of sulphates, phosphates and/or nitrates derived from the inorganic salt serving as the acid precursor. Such species may be present in the following quantities: * Greater than 500, 750, 1000 or 1500 mg/kg; and/or * Less than 5000, 4000 or 3000 mg/kg.

The presence of such species may be assessed in a leach test and provide an indication in the final product of the binder system used.

The quantity of binder in the finished product, particularly in the case of mineral * Greater than: l%, 2%, 2.5%, 3%, 3.5% or 4%; and/or * Less than: 20%, 15%, 10 % or 8% measured by dry weight of the finished product.

Particularly in the case of mineral fibre insulation, the products may have one or more of the following parting strengths: Ordinary Parting Strength of * At least 120 g/g, preferably at least 150 g/g; and/or * Less than 400 g/g Ordinary Parting Strength of * At least 120 g/g, preferably at least 150 g/g; and/or * Less than 400 g/g % loss between Ordinary and Weathered Parting Strength; and/or * Less than 10%, preferably less than 5% Embodiments of the invention will now be described by way of example.

Shell bone testing: Binders were prepared as aqueous solutions by * combining the ingredients of a desired binder formulation in an open, unheated reaction vessel * adding distilled water * subsequently adding a silane solution * agitating during addition of liquids and afterwards for several minutes to achieve complete dissolution of solids such that the binder solution contained approximately 50% dissolved solids as a percentage of total weight of solution. A 2-g sample of this solution, upon thermal curing at 400°F for 30 minutes, would yield 30% solids (the weight loss being attributed to dehydration during thermoset binder formation).

An evaluation of dry and "weathered" tensile strength of glass bead-containing shell bones provided an indication of the likely tensile strength and the likely durability of fibreglass insulation or other materials prepared with that particular binder. Predicted durability is based on the ratio of a shell bone's weathered tensile strength to its dry tensile strength.

To prepare the shell bones, an electric mixer was used for about two minutes to mix approximately 75 g of binder with 727.5g of glass beads (Quality Ballotini Impact Beads, Spec. AD, US Sieve 70-140, 106-212 micron-#7, from Potters Industries, Inc.). Any clumps from the sides of the mixer whisk and from the sides and bottom of the mixing bowl were mixed in manually using a spatula about half way through the mixing and also at the end of the mixing.

The prepared glass beads/binder mixture was added to the mould cavities of a shell bone mould (Dietert Foundry Testing Equipment; Heated Shell Curing Accessory, Model 366) which had been pre-heated to 425°F. The surface of the mixture in each cavity was flattened out, while scraping off the excess mixture to give a uniform surface area to the shell bone. Any inconsistencies or gaps that existed in any of the cavities were filled in with additional glass beads/binder mixture and then flattened out. The top platen was quickly placed onto the bottom platen (to avoid producing shell bones with two differentially cured layers). The cured shell bones were removed after seven minutes, cooled to room temperature on a wire rack, labelled and placed individually in plastic storage bags. If shell bones could not be tested on the day they were prepared, the shell bone-containing plastic bags were placed in a dessiccator unit. During curing the temperature of the bottom platen ranged from about 400°F to about 430°F, while the temperature of the top platen ranged from about 440° F to about 470 °F.

Procedure for testing breaking strength: * Equipment: 5500 R Instron machine * Immediately prior to testing, each shell bone was removed from is plastic bag and its weight and thickness recorded.

Weathering Procedure for Shell Bones: * 24 hours weathering in a pre-heated humidity chamber (Blue M humidity chamber, 90°F, 90% relative humidity) * upon removal shell bones were sealed in individual plastic storage bags and taken immediately for testing.

Procedure for measuring gel time: A small amount of binder (2.Oml) is added to the centre of a hot plate set to 150°C and a stop watch is started.The binder is worked with a spatula until it is possible to draw the sample into a long string. The time taken from the addition of the binder to the string formation is the gel time.

Binder formulations tested: Test ref: Binder formulation (by dry weight) A 85% DMH + 15% CA + 4.8% NH4OH + 0.3% 1S10200 B 90% DMH + 10% AmSO4 + 4.8% NH4OF-I + 0.3% 1S10200 C 85% DMH + 15% AmSO4 + 4.8% NH4OH + O.3% 1S10200 D 80% DMH + 20% AmSO4 + 4.8% NH4OH + 0.3% 1S10200 E 90% DMH + 10% AmPO4 + 4.8% NH4OH + 0.3% 1S10200 F 85% DMH + 15% AmPO4 + 4.8% NH4OH + 0.3% 1S10200 G 80% DMH + 20% AmPO4 + 4.8% NH4OH + 0.3% 1S10200 Key: DMH = Dextrose monohydrate CA= citric acid NH4OH= ammonium hydroxide 1S10200= silane AmSO4= ammonium sulphate AmPO4= ammonium phosphate Test results: Test ref Dry Weathered Loss in Gel time of pH of breaking breaking breaking binder binder strength strength strength solution (s) solution (Mn/rn2) (Mn/rn2) from just before weathering! mixing with % beads A 1, 455 1,567 -7,70 343 9,54 B 1,271 0,895 29,57 280 10,28 C 1,550 0,856 44,79 362 10,24 D 1,877 1,156 38,39 327 10,13 E 1,499 1,069 28,68 356 10,18 F 1,281 0,848 33,82 334 9,99 G 1,123 0,801 28,74 287 9,73 ComDarative testing on insulation Droduct: Comparative testing of binder systems on a mineral fibre insulation product gave the following results:

Binder tested Description Formulation

PF1 Comparative example -Resin, Urea, Lignin, Ammonia, standard phenol formaldehyde Silane binder AC1 Comparative example -Dextrose 85% Citric Acid ammonium citrate based 15% Ammonia 4.8% Silane binder O.3% Exl Example 1 of the present Dexrose 85% Ammonium invention Sulphate 15% Ammonia 48% Silane O.3% Product used glass wool fibre insulation product, nominal density 16 kg,/m3, for test: nominal thickness 75mm, nominal width 455mm I0 Binder content of test product LOT (Loss on ignition) %weight: Mean Binder LOT PF1 6,22% AC1 6,9l% Ext 6,78% Drape test (mean average in mm measured after the periods specified): Week Week Week Binder Day 1 1 3 6 PF1 55 68 60 71 ACt 83 99 80 72 Ext 66 76 66 75 Thickness (mean average in mm measured after the periods specified in accordance with British Standard BS EN 823:1995) _______ Week Week Week Binder Day 1 1 3 6 PF1 76,4 75,1 75,1 75,2 ACt 75,3 73,6 72,5 74 Ext 76 76,7 74,9 74,3 Density (mean average in kg/rn3 measured after the periods specified) Week Week Week Binder Day 1 1 3 6 PF1 16,44 16,7 16,35 16,44 ACt 16,68 16,41 16,33 16,48 Ext 16,5 16,9 16,5 16,5 Quantity of suiphates present mg/kg Sample Sample Binder 1 2 ACt 240 240 Exi 2000 2200 Parting strength (g/g) Binder Ordinary Weathered %loss PF1 248 107 56.85 ACt 230 199 13.47 Ext 196 189 3.57 Test procedures: Binder content LOT (Loss on ignition) A weighed sample of wool plus binder is placed in a muffle furnace set to 550°C. After a set time the wool is removed from the furnace, placed in a desiccator to cool and re-weighed. The weight loss is expressed as a percent:age of the original sample weight and is known as the binder content or Loss On Ignition (LOT).

Drape test A single ball (or slab) is placed across two poles (each 500mm long, 20mm diameter) set into a wall 1 metre apart. The degree of sag in the centre of the bait is recorded. This is repeated for all of the baits in a pack and for several packs. Packs are measured at set points over a period of time to determine the long term effects of compression on the balls.

Density: measured for the samples subjected to the drape test Quantity of sulphates present: leaching test for granular wastes in water with eluate analysis according to British standard BS EN 12457-2 at L/S10 Parting Strength The parting strength is expressed in grams/gram being the total breaking load of six test specimens divided by their total weight.

The test is carried out on mineral fibre mats as received for testing (Ordinary Parting Strength) and after an accelerated weathering test as explained below (Weathered Parting Strength).

A first set of six samples of the form and dimensions shown in Fig 1 are cut from the mineral fibre mat to be tested; the long axis of the samples should be parallel to the conveyor direction and the samples should be taken across the full width of the mineral mat. A second set of six samples is then taken in the same way. The dimensions in Fig 1 are in mm.

The total weight of the first group of six samples Wi in grams is recorded.

The total weight of the second group of six samples W2 in grams is recorded; these samples are then placed in a preheated autoclave and conditioned on a wire mesh shelf away from the bottom of the chamber under wet steam at 35kN/m2 for one hour. They are then removed, dried in an oven at 100°C for five minutes and tested immediately for parting strength.

To test the parting strength, each sample is mounted in turn on the jaws of a 5500 Instron tensile strength machine and the maximum breaking load in grams or Newtons is recorded. If the breaking load is measured in Newtons it is converted to grams by multiplying it by 101.9. Six results in grams are obtained for each set of samples: Gi G2 G3 G4 G5 and G6 for the first set of samples and G7 G8 G9 GlO Gil and G12 for the second set of samples.

The Ordinary Parting Strength is calculated from the first set of samples using the formula Ordinary Parting Strength = (Gl+G2+G3+G4+G5+G6)/Wl.

The Weathered Parting Strength is calculated from the second set of samples using the formula Weathered Parting Strength = (G7+G8�G9+G10�Gii�G12)/w2.

Claims

CLAIMS: 1 A substantially formaldehyde free binder solution having a pH of greater than 6 comprising -a carbohydrate, -an acid precursor derivable from an inorganic salt, and -a source of nitrogen.
2 A binder solution in accordance with claim 1, in which the binder comprises an aqueous solution comprising a carbohydrate and an inorganic ammonium salt.
3 A binder solution in accordance with any preceding claim, in which the carbohydrate is a reducing sugar, preferably dextrose.
4 A binder solution in accordance with any preceding claim, in which the acid precursor comprises a species selected from the group consisting of suiphates, phosphates and nitrates.
5 A binder solution in accordance with any preceding claim, in which the acid precursor comprises an ammonium salt.
6 A method of manufacturing a substantially formaldehyde free binder solution for binding a collection of loose matter comprising forming an aqueous solution having a pH of greater than 6 from a carbohydrate and an acid precursor comprising an inorganic ammonium salt.
7 A method in accordance with claim 6, in which the acid precursor makes up between 5% and 25% by dry weight of the binder solution.
8 A method in accordance with claim 7, in which the inorganic ammonium salt makes up between 5% and 25% by dry weight of the binder solution.
9 A method in accordance with any one of claims 6 to 8, in which the carbohydrate comprises a reducing sugar, preferably dextrose.
10 A method of manufacturing a product comprising the steps of: * Providing a collection of loose matter; * Treating the collection of loose matter with a substantially formaldehyde free binder solution having a pH of greater than 7 comprising: a carbohydrate, an acid precursor derivable from an inorganic salt and a source of nitrogen; * Arranging the collection of loose matter treated with the binder solution in the form of a substrate; * Curing the binder by applying a source of energy to the substrate.
11 A method in accordance with claim 10, in which the curing of the binder is carried out by passing the substrate through at least one zone of a curing oven at a temperature within the range 230 °C -300 °C for a time with an oven residence time in the range 30 seconds to 20 minutes.
12 A material comprising a collection loose matter maintained together by a substantially formaldehyde free binder characterised in that the material comprises more that 500 mg/kg of species selected from the group consisting of sulphates, phosphates and nitrates.
13 A material in accordance with claim 12 in which the species selected from the group consisting of sulphates, phosphates and nitrates is derived essentially from binder precursors.
14 A material in accordance with any of claims 12 to 13 in which the binder is cured and comprises melanoidins.
A material comprising a collection loose matter and uncured or partially cured substantially formaldehyde free binder characterised in that the binder has a pH of greater than 6 when dissolved in water and comprise a carbohydrate, an acid precursor derivable from an inorganic salt and a source of nitrogen.
16 A material in accordance with claim 12 or claim 15 in which the loose matter comprises mineral fibres.
17 A material in accordance with claim 16 in which the material is a mineral fibre thermal insulation material.
18 A material in accordance with any of claims 12 to 15 in which the material is a wood board.